The present invention relates to steam traps and more particularly to steam traps for expelling large quantities of condensate fluid at low pressures and for self locking in a closed position at pressures above a predetermined pressure.
Steam traps find many applications in steam systems. Such traps are necessary because when a steam system is started up, large amounts of condensate fluid are formed within the system conduits. Once a system reaches an on-stream normal operating condition, however, only small amounts of condensate are formed because the system conduits are heated to operating temperature and are generally well insulated. As an example, the ratio of condensate flow between system start up and the on-stream condition can be ten to one.
Steam systems generally include return lines which vent condensate fluid from the system conduits. The return lines, however, can be long and require the condensate to be lifted, necessitating high conduit pressure, in order for the system to vent the condensate. Under on-stream conditions, there generally is no problem because on-stream system pressures are generally high enough to vent the system of condensate and because only small amounts of condensate are produced.
However, during start up, large amounts of condensate are formed and the system is at low pressure. It is not unusual, therefore, for the system to be unable to vent the condensate formed during start up. This can cause a number of problems including, for example, blockage of the system conduits and ultimate conduit rupture or condensate back-up within the conduits into heating coils which are expensive to replace. What is required in such applications therefore is a steam trap which can expel large quantities of condensate fluid at low pressures and which can self lock closed at pressures above a predetermined pressure, such as at or slightly below the on-stream pressure of the steam system.